The essential role of Btk in autoimmune disease is underlined by the observations that Btk-deficient mice are protected in standard preclinical models for rheumatoid arthritis (Jansson & Holmdahl 1993), systemic lupus erythematosus (Steinberg et al. 1982), as well as allergic disease and anaphylaxis (Hata et al. 1998). In addition, many cancers and lymphomas express Btk and appear to be dependent on Btk function (Davis et al. 2010). The role of BTK in diseases including autoimmunity, inflammation and cancer has been recently reviewed (Tan et al. 2013; Rickert 2013).